Canberra
Water overview

During the 2012–13 year the Cotter Reservoir was enlarged to increase its storage capacity. The project commenced in 2009 to increase the total capacity from 3,856 ML to 79,375 ML to deal with frequent, longer and severe droughts without implementing high-level water restrictions for extended periods.The project successfully completed and the reservoir began impounding water on 1 March 2013.

The flow volume in the Queanbeyan River during October 2012 was significantly high and well above long-term mean monthly flow (see below).

There are five major rivers within the Canberra region:

• Cotter
• Gudgenby
• Molonglo
• Murrumbidgee
• Queanbeyan.

The Murrumbidgee is the major river system that flows through the Canberra region within the Murray–Darling Basin, with all rivers and creeks in the Canberra region draining into the Murrumbidgee River.

During the 2012–13 year rainfall across the Canberra region was generally below-average except for January, February and June (see Climate overview). As a result, streamflows in the Cotter and Molonglo rivers were low compared to the long-term mean annual flow. The total annual flow in Quenbeyan River was slightly above the long-term mean annual flow.

Figures W1, W2 and W3 show the monthly flow volumes at the gauging stations of Molonglo River, Cotter River, and Queanbeyan River for the 2012–13 year.

The monthly flow in October 2012 was remarkably high in Molonglo River and Queanbeyan River. It can be due to the flow diversions to reservoirs.


Figure W1 Monthly flow of the Molonglo River at flow gauging station 410705

There are three key water storages located on the Cotter River: the Corin, Bendora, and Cotter reservoirs. They supply urban water for the Canberra region. Figure W2 shows flows down the Cotter River at gauge 410730 located upstream of the Corin Reservoir. These flows enter the Corin Reservoir where water is released or spilled flows downstream to the Bendora Reservoir and eventually to the Cotter Reservoir. 

Figure W2 Monthly flow of the Cotter River at flow gauging station 410730
   

The Queanbeyan River is a tributary of the Murrumbidgee River, and significant in the context of the Canberra region because the Googong Reservoir is located on it, southeast of Queanbeyan. High inflows into the Googong catchment saw increased streamflows and runoff into storage in the 2012–13 year.

Figure W3 Monthly flow of the Queanbeyan River at flow gauging station 410781

Australian Capital Territory (ACT)

Following the National Plan for Water Security (2007), the ACT Government announced a range of new water supply projects that ACTEW Water continued to implement throughout the 2012–13 year.

These include:

• Enlarging Cotter Reservoir to increase the total capacity to 79,375 ML: Construction of this project commenced late 2009 and was expected to be completed in 2012 but significant rain events and flooding in 2012 delayed construction. The reservoir began impounding water on 1 March 2013 and has since allowed total storage in the ACT to exceed the previous capacity.However, even with average inflows it will take over 2 years for the storage to reach full capacity.
• The Murrumbidgee to Googong water transfer pipeline: This will allow the transfer of water from the Murrumbidgee River to Burra Creek, where it will flow into Googong Reservoir. Planning for this transfer continued during the 2010–11 year and construction commenced in early 2011. The Murrumbidgee to Googong water transfer was completed in August 2012 but has not been operated except for maintenance purposes.
• ACTEW Water has purchased an additional 5,404 ML of high security entitlements to bring the total to 9,549 ML along with 12,523 ML of general security entitlements. These water entitlements are from the NSW Regulated Murrumbidgee River and are to be utilised under the Tantangara Transfer Option. This option is to be available for use only during extreme droughts.
• In October 2007, the ACT Government announced a range of new water supply projects for the ACT region, including the design of a Demonstration Water Purification Plant. ACTEW Water completed the design, but construction has been deferred subject to the successful implementation of the other three water security projects (Enlarged Cotter Dam, Murrumbidgee to Googong Pipeline and the Tantangara Transfer Option). ACTEW Water will continue to monitor water storage levels, rainfall and inflows to determine whether water purification is required to help secure future water supply. 

New South Wales (NSW)

The water sharing plan for the Murrumbidgee Unregulated and Alluvial Water Sources, which covers the area of the Canberra region, commenced on 4 October 2012.

The Water Sharing Plan for the NSW Murray–Darling Basin Fractured Rock Groundwater Sources also commenced on 16 January 2012. This water sharing plan is due for extension/replacement in July 2022. In 2020, when the Peel Valley Water Sharing Plan is due for remake, and in 2012 when the North Western NSW Water Sharing Plan is due for revision, the fractured rock groundwater sources within these plans will be merged with this plan. This would result in a single water sharing plan covering the inland fractured rock groundwater sources.

Commonwealth

The Murray–Darlin Basin Plan was finalised in May 2012 for the Minister for Sustainability, Environment, Water, Population and Communities to adopt it in November 2012. One of the key elements of  the basin plan is the setting of new limits, sustainable diversion limits (SDLs), on the amount of water used in the basin. Sustainable diversion limits will be enforced through state water resource plans and fractured rock groundwater sources.The plan has specified a long-term sustainable diversion limit of 10,873 GL/y. This would provide an additional 2,750 GL/y of water returned to the basin's rivers

The Murray–Darling Basin has been divided into 29 surface water SDL resource units and 66 Groundwater SDL resource units. Surface-water SDL resource unit SS1 and Groundwater SDL resource unit GS52 cover the ACT. The remaining area of Canberra subaccount region is within surface water SDL resource unit SS15 Murrumbidgee and Groundwater SDL resource unit GS20 Lachlan Fold Belt. The share of the 2,750 GL/y to be returned from the SS1 and SS15 regions is yet to be determined.